Emergency personal breathing systems have been proposed and offered in the past. One such system is described and illustrated in U.S. Pat. No. 5,394,867, of common assignee herewith. In the system described in that patent, a canister is provided for disposition in and deployment from an overhead compartment in an aircraft. The canister includes a filtration unit containing filtering material, a hood and a mouthpiece, including an attached nose clip, the housing being closed at one end by a cover. The canister also includes an air flow conduit bypassing the filtration unit and connected at the opposite end of the canister to an external source of air, i.e., an oxygen supply. The filtration unit in that canister includes layers of activated charcoal granules, a desiccant and a catalyst for the catalyzation of carbon monoxide to carbon dioxide, each layer being preferably separated by an electrostatically charged fabric filter for collecting particulate matter. Also, a layer of lithium peroxide or other suitable chemical may comprise a fourth layer for converting carbon dioxide to oxygen.
In that system, the canister includes a hood and a mouthpiece which are deployable from the canister upon removing the canister cover. The mouthpiece contains a one-way inhalation check valve and two one-way exhalation check valves and carries a nose clip. The mouthpiece and nose clip are enclosed within a wholly transparent flame and heat-resistant hood, preferably having a titanium coating sufficient to provide required reflection and transmission properties but sufficiently thin to afford visibility through the hood. A hood of this type is disclosed in U.S. Pat. No. 5,113,527, licensed to assignee of the present invention.
The canister of U.S. Pat. No. 5,394,867 also includes an air flow conduit which bypasses the flow of ambient air through the filtration unit and supplies air to the user of the personal emergency system from the aircraft's air supply. Thus, when the canister is deployed from the compartment in the aircraft, the aircraft air supply delivers breathable air from the external source directly to the mouthpiece, bypassing the filtration unit. The air flow inlet from the aircraft air supply has a quick connect/disconnect coupling enabling rapid disconnection of the canister from the aircraft air supply upon evacuation from the aircraft. Upon disconnection and evacuation, the individual breathes filtered ambient air. Exhalation air passes through the exhalation check valve of the mouthpiece into the hood for egress into the surrounding environment through the space between the margin of the hood and the individual's neck.
While that system is effective for use in an aircraft where it may remain connected to the aircraft's oxygen supply, it is not suitable for use in escaping from other confined spaces having resident toxic gases or smoke from a fire. For example, escape from confined spaces on ships which may contain toxic gases and/or smoke or oxygen-depleted atmospheres has been recognized as a problem for many years. Currently used devices to effect escape from the confined spaces on board a ship require an individual to move unprotected to a cache of SEED units, don the SEED units which provide a limited amount of oxygen for a very short duration, then locate and move to a cache of EEBD (emergency escape breathing device) units, exchange the SEED units for the EEBD units which generate oxygen via a chemical process, don the EEBD unit and move on to escape from the toxic gas, oxygen-deficient or smoke-filled space. This procedure is not only time-consuming but employs hazardous material. Also, those oxygen-generating systems use potassium superoxide canisters which, when mechanically actuated, cannot be stopped or controlled. A significant amount of heat is also generated by these devices once activated and have injured many users employing the system. The materials used in the EEBD system are hazardous and become unstable over time, introducing a potential source of explosion or fire, e.g., especially if the system becomes wet, on board a ship. They are also classified as HAZMAT and consequently are difficult to disperse and require controlled and costly disposal. Thus, there has developed a need for further improvements in personal breathing systems for escape from toxic gas or smoke-filled environments.